Mixture control for airplane carburetors



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Patented July 19, 1927.,

rRANKc. mock; CHARLES. .r. Gusrarsouj a 1,636,480 UNKI'TEDQSTATESPATENT OFFICE.

AND IlIiILTON n. cIIAnnLEn, or CHICAGO, ILLIuoIs, AssIeNo'ns .TO s'rnomnnne moron nzavrons comrm, or CHICAGO, ILLINOIS, A. conroRA'rIoN or ILL NOIS.

MIXTURE CONTROL son AIItPLANE omunn'rons.

Original application filed July 10, I918, Serial'No. 244,231. 'Divided and this application med April 5,

, 1 1 1920. serial'm. 371,199.

' Our invention relates to mixture control for. airplane engines, and this application maybe considered as covering a division of the'subject matter disclosed in'our application, Serial No. 244,231 filed July 10, 1918.

In the operation ofairplanes, the'changes in temperature and air density encountered as the altitude varieshave made it imperative that the carburetor structure should be adapted to meet these-conditions, especially with regard tothe delivery of fuel to the main discharge means. It has been found that as an ordinary carburetor is introduced into an area in which the air pressure is reduced, the mixture has a tendency to become enriched to an undesirable degree and extensive use of carburetors on air craft has proven that the proportion of air to fuel is reduced as the air density, decreases Th1s 15 due to the fact that as the pressure decreases,

I the air becomes rarer and the air content in the mixture decreases.

In accordance with our invention we provide means for controlling the fuel delivery directly in proportion to theair, so that at all times the proper mixture may be-.produced. -;This we accomplish by'connecting the fuel chamber with a region of suction in 'the carbureting chamber, so as to act uponthe fuel contained therein. By controlling .the degree of suction applied to the fuel chamber the fueldelivered therefrom to the main discharge means may be regulated to a nicety.

I The control of the degree or absence of the, suction in the. fuel. chamber we accomplish by admitting air'into the fuel chamber or the suction connection between the carburet ing chamber and the fuel chamber and by this means the suction eflect may be neutralized entirely or. to any degree. 'When the carburetor is in an atmosphere of normal or sea level pressure ai'ris admitted to the suction line and as the airplane rises'and the air density decreases air will be excluded more or less from the suction line.

lVe provide for the automatic control? of the air bleed by barometric control means and we also provide for manual control in connection with such automatic coritrol.

The barometric control means lltland such leakage would result in the mixture being .very lean as the air ,planei approaches the ground, with possibility of serious danger unless the pilotbe given some means for cutting olf or modifying the action of the automatic means if the ease should arise. A leaky or improperly operating barometric means would also result in the fuel consumption being unduly rapid in altitude flights We have-therefore devised a manual air controlling means by which the pilot may test, correct and adjust the mixture proportions whenever the automatic control is not functioningeflicient-ly or propmanually therewith for regulating the 'air bleed into the suction line to the fuel chamber; Fig. 2, is an enlarged plan view of the manually In the carburetor structure" shown 10 Fig. 1, more or,

n retor and barometric control means andcontrollable I means, associated l controllable 'valve'structureand 3, is an. enlarged sectional view on plan 3-3 Fig. 1.'

designates the main barrel or mixing chamher which has a lateral extension forming the main air inlet 11, the inletbeing prefer-' ably large to admit air freely and in large quantities when atal'tit-udes at which the density of the air is decreased. A throttle valve 12 is mounted'in thebarrel 10 for controlling the flow of air into the engine. A

double Venturi structure is shown comprising the large venturi 13 and the smaller veninto the smaller venturi from the supporting boss 16, forming part of the carburetor framework: Fuel is delivered to the nozzle from the. float chamber 17 by way of the 'passagewayi18 and the calibrated orifice 19.

.The float 20 is of the conventional type and operates. the valve 21*for controllin the inflow of fuel to the inlet 22 and there y regulgatingth'e level of the fuel in the float chami A suction passageway 23 communicates at its outenend with the top of the float chamturi 1.4, the fuelsupply nozzle 15 extending her thru the restricted orifice 24, the inner end of this passageway communicating with the space between the large venturi and the adjacent wall of the carbureting space .10, the ports 26 connecting the space 25 with the interior of the venturi at the throat of the venturi. When the carburetor is in operation suction effect from the engine is communicated through the ports 26 to the space 25 and from there to the passageway .23 to the top of the float chamberabove the fuel therein. Such construction will tend to re tard the flow of fuel from the float chamber 7 .rtends to the manually controllable valve 2O ment 30,

a being servedby the carburetor.

to the main nozzle 15. s

A threaded nipple 27 extends from the top. of'the float chamber frame and communicates with the'suction passageway 23. A duct 28 connects with this nipple and exstructure designated as a whole M. This valve structure may be remote from the carburetor and is shown as secured to a supporting wall 29 which may bethe instrumentboard on the airplane whose engine is The barometric-control device B may also be remote from the carburetor and as shown may also be mounted on the wall 29. The barometric device is shown more or less diagrammatically. It comprises the barometric member or shell 30 shown inthe form of an expansible bellows which seats against the base 31 of' the enclosing and protecting case or cage 32. A plate 33 is secured to the outer end of the bellows and hasthe plunger extension 34 engaging in the cylindrical guide operation with the seat 41 to control the flow of air into the duct 42 which is adapted to be connected with the duct, 28 thru the valve structure M. Air enters the valve chamber thru the inlets-43. The baro- .metric element 30 is filled with ,dry air at sea level temperature and pressureand the valve controlled thereby is open when the atmosphere surrounding the barometric element is of the same temperature and pressure: However, when the airplane rises and the atmospheric pressure decreases the bare? metric member will expand and move. the valve toward or into closing position.

' Describing now the valve structure M, its fraine comprises the base 44 and the top 45, The top has the valve chamber 46 with which connects the duct 28 leadin to the float chamber of the carburetor. Wlthin the Lassa so valve chamber and seating on'the base 44 is the plate 47 on top of which the valve disc 48 is rotatable. ljhe rotational movement of the valve disc is guided by its' hollow. stem 49 which is journaled in the" base 44. The cover journals a shaft 50 to the gpter end of which is secured the hand wheel 52 for receiving the projections. 53 on the valve disc so that this disc will turn withthe" shaft. -A spring 54 enters into the hollow. valve stem 49 and also into the recess 55 in the lower end ,of the shaft and this spring tends to hold the valve'disc against 1ts seat. A spring clip 56 frictionally ens gages the periphery of the hand wheel and serves to lock it in adjustedposition.

A passageway 57 extends radially into the valve structure base 44 and connects with a port 58 thru the base and the valve seat plate 47. The air pipe 42' extends from the barometric controlling device B is connected with the passageway 57.. The valve disc has the segmental port 59 for controlling the opening and closing of the port 58.

Extending in axial direction thru the. valvestructure base is the passageway 60 The inner end of'the shaft has notches" which, at its inner end, connects with the port 61 thru the'seat plate 47 and, in the outer end of this passageway is secured the duct 62 which terminates in the air intake 11 of the carburetor structure. A circular port 63 in the valve disc controls the opening and closing of the port 61 as the valve is rotated. Stop lugs 64 and 65 on the frame 45 are engaged bythe post 66 of the hand wheel to limit the rotational" movement of the valve disc. 4 Describing now the operation, in the position shown on the drawing the passageways 57 and 60 are connected thru the valve ports i with the valve chamber 46 so that the carburetor float chamber will receive its maximum supply of bleeding air, partiof the air flow being from the barometrically controlled device by way of the duct 42, the

-valve structure, and the duct 28, and the balance of the air supply being-from the carburetor air inlet by way of the duct 62, the valve structure, and the duct 28. By

vrotating the hand wheel and the valvedisrr in counterclockwise direction (Fig. 2) the connection of the air supply from the carburetor air inlet may beshut-ofl' to any desired degree as the valve '63 moves away from the -port 45. Solong as the elongated or segmental ,valve port 59 connects with the port 58 air will flow through-the float chamher from the barometric device. The counterclockwise rotation of the valve disc is stopped bythe engagement of the post 66 with the stop lug 64, the endof the valve port 59 being at this time still in communication with the port 58. Thus while the automatic air supply is fully openthe manual controlled supply can be increased or diminished or entirely out ofi, as desired. The automatic control of the air supply can thus be left entirely in full charge or this air supply may be modified by the operation of the manual control.

lVhen the valve disc is turned in clockwise direction from the position shown in the drawing the ports 58 and 61 will be gradually closed and when the post 66 reaches the stop 65 the ports will be entirely closed and all air flow will be shut off from the float chamber. In advance of such full closure of the ports they may be simultaneously opened or closed to any degree desired. If the stops 64: and 65 were removed the valve could be turned to shut off the automatic air supply and the air supply to the float chamber could be controlled entirely manually.

The automatic mixture control is very useful in single pilot combat planes where the attention of the pilot is required on so many other things that he does not have time to correct the mixture. It is impractical to attempt to set the automatic control to give the most economical mixture possible because this is too close to a condition where the engine might start to miss fire if some of its elements are not functioning properly, and so the automatic control is given a margin of richness or a factor of safety. There are conditions, however, such as long flights over land and sea, where the pilot is anxious to conserve his supply of fuel to the utmost and has time to adjust the mixture to the leanest possible point. It is very important that he should be able to do this without interfering with the setting of the automatic control or its operation, and a manual control such as has been described is efliciently adapted for this purpose, the operator bein able to manually adjust for the desired air-bleed to the fuel chamber.

,Another situation quite often encountered is when the engine starts to miss fire in the air which may be the result of the partial stoppage of the fuel jet of the carburetor,

a sticking of the automatic control, or some reason entirely separate from the fuel system. The pilot will, of course, wish to test so far as he can the various controls which he has, such as ignition switches, the gasoline fuel feed system, and the action of the automatic control itself. Using the manual valve mechanism, the pilot can tell definitely Whether the automatic control is at fault and the amount it is at fault, and can govern his course of action accordingly, whether to land immediately or try to keep in the air, and so on. Thus there is a real practical advantage from the use of a manual control in co-operation with the automatic control. I

We claim the following In an altitude mixture control for airplane engines, in combination, a carburetor of the common type having a carbureting passageway and a constant level fuel chamber, a connection for communication of suction between the air space in said fuel chamber and a point of suction in said passageway, an air passageway leading from a region of atmospheric pressure to-the air FRANK o. MOGK. CHARLES J. GUSTAFSON. MILTON E. CHANDLER. 

